Introduction: The United Utilities AMP5 Process Alliance Partner, Gallliford Try–Costain–Atkins Joint Venture (GCA JV), together with Powerrun Project Management Ltd their selected Tier 2 pipework fabrication specialist based in Keighley, West Yorkshire have recently achieved a significant milestone on the £200million Liverpool Project, with the successful completion of almost 400m of very large diameter, fabricated steel and ductile iron pipework ranging from 1600mm – 2200mm diameter. The project has employed Building Information Modelling throughout, which has enabled the design and construction team to fabricate, coat and install the pipework to extremely close tolerances. With no on site cutting allowed, due to the coating on the Powerrun Project Management Ltd supplied fabricated steel pipework, the installation contractors were anxious that such a large diameter network, running hundreds of metres with fixed points, could be laid without significant on site modifications.
Design: Utilising the granularity of the 3D BIM model, the design team modelled a conceptual layout, for review. Once pipe materials had been finalised, and both internal and external diameters established, the layout was rationalised and the 3D model revised, to include wall thicknesses and joint details (including setting gaps at joints). In close consultation with Powerrun Project Management Ltd extremely careful consideration was also given to circularity and diameter tolerances, matching different pipe materials and ensuring that couplers fitted perfectly (accepting +/- 5mm circular pipe tolerance).
Fabrication: A copy of the federated 3D BIM model was issued to Powerrun Project Management Ltd our specialist pipework fabrication contractor, who was able to interrogate it for exact dimensions, to enable completion of 2D fabrication drawings, which were then returned to the GCA design team for checking. Each individual fitting was then extracted from the model, rotated to horizontal and flattened to check the two versions against each other, on check completion and sign off, the go ahead was given to Powerrun Project Management Ltd for fabrication of the fitting.
All of the 1600mm, 2000mm and 2200mm diameter pipework was fabricated by Powerrun Project Management Ltd from 20mm thick carbon steel material with the largest single pipe spool being 2000mm in diameter x 11000mm long and weighing 11,300Kgs.
The attention to detail and due diligence demonstrated by Powerrun Project Management Ltd during the fabrication and coating process was an invaluable contribution to the smooth and unhindered installation process at site.
Construction: Working closely with the 3D BIM design team, GCA Site Engineering carefully monitored each invert level and centreline co-ordinates at joint locations. With the design team able to interrogate the model at any point during the construction phase, site supervisors were provided with all the information they required to replicate the model exactly.
GCA JV Senior Civil Engineer, Patrick Wills explains, “We couldn’t have achieved the levels of fabrication accuracy without the co-ordinated 3D BIM model. Fabricating steel pipe at very large diameters to the required accuracy is a difficult process, starting out with accurate dimensional data and following it through with a structured checking system lead to project success”.
GCA JV 3D CAD Manager, Matt Lees noted, “This is a true testament to the collaboration of design and construction. A lot of thought went into the virtual version of what you see here. In the first instance, each piece was modelled granularly then flattened and exported to help create the 2D fabrication details. Powerrun Project Management Ltd produced pipe spool fabrication drawings were then back checked against the 3D model”.
GCA JV Senior Engineer, Gregory Hood added, “Constructing the large diameter pipework was a collaborative process from start to finish. With the use of BIM along with early involvement of the construction team and Powerrun Project Management Ltd our chosen pipework fabrication specialist, we were able to not only value engineer the scheme but plan for the safe installation of the large sections of pipework and precisely install each individual piece of the project”.
Powerrun Project Management Ltd also engaged the services of Corrocoat Ltd of Leeds who carried out the application of the Armagel, Polyglass VEF and Corrocoat ZIP E coatings and Viking Johnson Ltd for the supply of the large diameter flange adaptors and couplings.